The sport debuted in San Diego, California, on September 25, 1974, when a race organized by local athletes Jack Johnstone and Don Shanahan was dubbed a triathlon. The event saw 46 competitors swim 460 metres (500 yards), run 9.6 km (6 miles), and bike 8 km (5 miles). Several years later John Collins, a U.S. Navy officer stationed in Hawaii who had finished 35th in the San Diego race, established the Hawaiian Ironman. That triathlon begins with a 3.8-km (2.4-mile) swim, followed by a 180-km (112-mile) bicycle ride and a 42-km (26.2-mile) run (the equivalent of a marathon). Only 15 athletes participated in the inaugural Hawaiian Ironman triathlon, but the race quickly gained international attention and became the sport’s premier competition. At the beginning of the 21st century, the Hawaiian Ironman regularly attracted some 1,600 competitors representing more than 50 countries.

While triathlons were initially sponsored by local clubs, the more important races, including the Hawaiian Ironman, soon began to garner corporate sponsorships. In 1989 the International Triathlon Union (ITU), the sport’s official governing body, was founded in Avignon, France, with the mission to promote the sport’s global appeal. The ITU hosts an annual World Championship.

Triathlons may vary in length, but all begin with swimming, followed by cycling, and end with running. The Olympic and ITU championship triathlons consist of a 1.5-km (0.9-mile) swim, a 40-km (25-mile) bike ride, and a 10-km (6-mile) run. The top men typically finish in about 1 hour 50 minutes, the women in just over 2 hours. “Sprint” versions of the triathlon include a swim of up to 1 km (0.6 mile), a bicycle ride of up to 25 km (15.5 miles), and a run of up to 5 km (3 mile), while “long” contests can involve a 2- to 4-km (1- to 2.5-mile) swim, 50- to 100-km (31- to 62-mile) bicycle ride, and a 10- to 30-km (6- to 19-mile) run.

The one-day triathlon that covers the longest distances is the Ironman, which top performers finish in less than nine hours. Planners continue to organize longer unofficial races as participants become more ambitious to test the limits of human endurance. In 1998 Monterrey, Mexico, hosted a double deca-triathlon, an event 20 times as long as the Ironman. Lithuanian Vidmantas Urbonas won, completing the race in under 438 hours.